This invention pertains to devices and methods for testing eyes. More specifically this invention is directed to methods an automated system for determining refractive errors of the eye.
Testing refractive errors of the eye involves several tests, some of which are subjective, and other that are objective in nature. Objective refraction tests include the use of well known retinoscopy and autorefractors, while subjective refractions include a variety of tests that determine sphere, cylinder and axis. In these subjective tests targets are presented to a subject with a projector, or with illuminated wall charts. Lenses are changed manually using a manual phoropter, for example see U.S. Pat. No. 5,223,864 (Twisselmann, issued Jun. 29, 1993) or trial frames. With these manual methods, several procedures are subject to interpretation and error due to their subjective nature of implementation. Furthermore, a highly trained specialist is required to conduct these tests.
More recently efforts have been directed to the use of automated devices for the testing of refractive errors of the eye. Such devices include autorefractors, autolensometers, and autophoropters. For example U.S. Pat. No. 3,880,501 (Munnerlyn, issued Apr. 29, 1975) discloses a system for measuring refraction of eye that can be used manually or with automated refractors. U.S. Pat. No. 5,329,322 (Yancey, issued Jul. 12, 1994) discloses an autorefractor use to obtain refractions objectively and in a rapid manner using two images, and their reflected images, for differential comparison. A phoropter that can be manipulated by a control unit so that an operators movement can be minimized during the testing procedure (see for example U.S. Pat. No. 4,861,156, Terry issued Aug. 29, 1989) has also been disclosed. Shalon and Pund (U.S. Pat. No. 5,331,394, issued Jul. 19, 1994) disclose an autolensometer.
Several devices have been disclosed that further automate and reduce the subjective nature of eye testing. U.K. 2,129,963 (Munnerlyn, published May 23, 1984) discloses an autorefractor that is interfaced with a computer and its method of use. The method involves providing a moving spot of light that varies in brightness, and recording the response of the patient's eye by video. E.P. 568,081 (Wutz et al, published Nov. 3, 1993) teaches of an eye testing device that uses a phoropter or refractometer interfaced with a computer that receives data and controls the function of the associated device. However, the process for testing eyes is essentially the same as that carried out in a regular eye test, and the process is simply computer controlled. The eye test procedure of Wutz et al. is still performed by a specialist, it exhibits minimal time saving benefits over conventional "hands-on" eye testing procedures, and involves several subjective testing procedures that are capable of introducing error into the final result. Preussner (WO 93/01744, published Jun. 27, 1992) discloses a computer controlled eye testing system to automate the eye testing procedure. The system incorporates the use of a computer that:
1) controls an autophoropter to place lenses in front of a subject, PA1 2) directs test symbol displays, PA1 3) queries the subject via an acoustic unit, and PA1 4) determines the response by the subject via electronic keypad inputs. PA1 1) removal of subjective analysis from eye test procedure; PA1 2) produces a set of data easily interpreted by a refractionist; PA1 3) produces more consistent lens prescriptions as denoted by fewer subjects requiring adjustments to their prescriptions; PA1 4) permits the test procedure to be carried out by a technician without the need for a refractionist being present; PA1 5) produces an output suitable for interpretation by a refractionist, optician, or ophthalmologist thereby permitting eye tests to take place in remote locations which otherwise do not have access to qualified specialists; PA1 6) increases the time efficiency of the regular eye test procedure several fold. PA1 1) Obtaining autorefractor, corrected autorefractor, and autolensometer results; PA1 2) Calculating sphere; PA1 3) Performing a Red-Green test; PA1 4) Calculating cylinder and axis; PA1 5) Determining minimum cylinder power; PA1 6) Determining final sphere; and PA1 7) Recording all data. PA1 i) Obtain autorefractor and autolensometer results from file PA1 ii) Apply regression equations for sphere cylinder and axis to these results in the autorefractor results. PA1 i) Calculating the spherical equivalent of regression corrected autorefractor result; PA1 ii) Determining the expected unaided visual acuity using a visual acuity formula; PA1 iii) Displaying a single letter of a size corresponding to that obtained in step ii) is presented to the subject; PA1 iv) Determining if the response of a subject to the display of step iii) is correct or wrong; PA1 v) Determining whether regression corrected autorefractor result (obtained from step i)) is myopic, and unaided acuity is better than largest letter available, if yes then proceed to step ix), other wise, proceed to step vi). PA1 vi) Adding +2.00 diopter sphere to regression corrected autorefractor sphere. PA1 vii) Sending the sphere, obtained from step vi), along with the regression corrected autorefractor cylinder and axis to the phoropter. PA1 viii) Testing for visual acuity as in step iv) and storing the best visual acuity; PA1 ix) Calculating spherical equivalent using the visual acuity formula (i.e. no cylinder and axis); PA1 x) Converting the spherical equivalent to full correction (i.e. including sphere, cylinder and axis) using corrected autorefractor cylinder and axis result (obtained from step 1); PA1 xi) Sending the full prescription to the autophoropter. PA1 i) A red-green test target consisting of two identical test type line of letters, one set on a red background the other on a green background is displayed using a display device. PA1 ii) Subject is queried as to whether: PA1 subjects responses are entered using a keyboard or other input device. PA1 iii) Lens change is sent to autophoropter of plus or minus 0.25 diopter according to response obtained in (step ii): if the result is: PA1 a) then add -0.25 diopters to spherical power currently present in the autophoropter and send this spherical lens change to the autophoropter; or PA1 b) then add +0.25 diopters to spherical power currently present in the autophoropter and send the spherical lens change to autophoropter; or PA1 c) then add -0.25 diopters to spherical power currently present in the autophoropter and send the spherical lens change to autophoropter; and PA1 iv) If response changes from red to green, then end test; otherwise, PA1 v) If response changes from green to red, add -0.25 diopter to spherical power currently present in autophoropter and send this spherical lens to autophoropter and end test; PA1 vi) If response changes from red to same to green, end test; PA1 vii) If response changes from green to same to red, then add -0.25 diopter to spherical power currently present in autophoropter, and send this spherical lens to autophoropter and end test; PA1 viii) If response changes from same to red, add -0.25 diopters to spherical power present at the start of the test and send this spherical lens change to autophoropter and repeat test from step i); PA1 ix) If response changes from same to green, add +0.25 diopters to spherical power present at the start of the test and send this spherical lens change to the autophoropter and repeat test from step i); PA1 x) If three consecutive responses of either red, green or same are obtained, then display a line of test types with a white background on the display device and send initial and final spherical lens to the autophoropter; PA1 xi) Determine subjects's preference for clarity between these two lenses as entered from the keyboard or other input device, retain preferred lens in autophoropter, and end test. PA1 i) Determining axis at which to set testing lens from axis of cylinder present in the phoropter; PA1 ii) Using a standard lens addition formula add testing cylinder power (+4 diopters) and axis obtained from i) to sphere cylinder and axis present in autophoropter; PA1 iii) Sending this lens combination to autophoropter; PA1 iv) Setting the angle of cylinder and axis test target to 90.degree. to angle determined in step i) and displaying on a display device; PA1 v) Obtaining subjects responses using a keyboard or other device as to which line appears darker; PA1 vi) Determining whether the response is the more clockwise line, if so then rotate target 3 degrees clockwise, or if the response is the more counter clockwise line, then rotate the target 3 degrees counter clockwise; PA1 vii) Determining subjects response to a new position of the two lined astigmatic fan target; PA1 viii) Continuing with the above test to obtain first final angle until either; PA1 ix) Recording the first final angle on file; PA1 x) Determining new axis for testing lens 45 degrees from first axis (derived from step i) and repeat steps i) to ix) to obtain second final angle, and record on file; PA1 xi) Determining subjects residual astigmatic correction using the first and second final angles obtained in steps ix) and x) and the testing lenses spheres cylinders and axes; PA1 xii) Obtaining the corrected residual astigmatic correction by applying the least cylinder power regression equation to the residual astigmatic correction derived from step xi); PA1 xiii) Determining the calculated sphere, cylinder, and axis by adding the residual astigmatic correction (obtained from step xi)) to initial sphere cylinder and axis, using the lens addition formula; PA1 xiv) Determining the regression-corrected-calculated sphere, cylinder, and axis by adding the corrected residual astigmatic correction (obtained from step xi) to the initial sphere, cylinder and axis (obtained in step 3, the red-green test result) using the lens addition formula and send this information is sent to the autophoropter; PA1 xv) Displaying a line of test types on a display device; PA1 xvi) Determining subjects preference for clarity of test types to both the initial sphere, cylinder and axis (obtained in step 3, the red-green test result), and to the regression-corrected-calculated sphere, cylinder, and axis (determined in step xiv)); PA1 xvii) Repeating step xvi) using the regression-corrected-calculated sphere, cylinder, and axis (determined in step xiv) and the calculated cylinder and axis (determined in step xiii) and store preferred lens combination in phoropter and end procedure. PA1 i) Displaying a line of test type on a display device; PA1 ii) Determining minimum effective cylinder power by obtaining subject's preferences for clarity between 0.25 diopter changes in cylinder power; and PA1 iii) Selecting lower cylinder power when no preference is obtained when end point reached end test. PA1 i) Obtaining subjects visual acuity from correct or wrong reading of test types; PA1 ii) Determining subject's preference between present (determined in step 4, xvi) or step xvii)) lens combination and a modified lens combination comprising the same lens combination with +0.25 sphere added when sent to phoropter; PA1 iii) Determining subject's preference between present (determined in step ii)) lens combination and a modified lens combination comprising the same lens combination with -0.25 sphere added when sent to phoropter; PA1 iv) Determining visual acuity, if it is not 20/20 then reduce type size by one Snellen unit and proceed to step v), if visual acuity is 20/20 or better, end procedure; PA1 v) Determining subject's response to reading test type as correct or wrong; PA1 wherein the computer is capable of querying and receiving data from the autorefractor, autolensometer, autophoropter, and a subject, and based on the responses obtained from the subject, the computer is capable of controlling the autophoropter; PA1 wherein the querying and receiving data from the subject, and controlling the autorefractor, autolensometer, or autophoropter include: PA1 wherein steps 2 and 4 are as defined above.
This procedure, although more automated than that of Wutz et al in that it no longer requires a specialist for its operation, is still an automation of the conventional eye test procedure. Therefore, there is a need to develop methods and associated systems and devices that can be automated to reduce the subjective nature of the eye test procedure and that streamline the test procedure as well. Wutz et al or Preussner do not disclose new process steps to modify the eye test procedure, therefore, it is estimated that these procedures would take approximately 1 hour to complete. However, the procedure of this invention is complete within a 10 minute period of time. This time saving is due to the removal of the subjective testing and their replacement with novel tests that calculate refractive error.
With the method and system of this invention the operator makes no decisions regarding the progress or results of the test, thereby reducing the subjective nature of these tests. It is desirable that the outcome of these tests be in a form that is readily utilized by a specialist such as a refractionist for the preparation of suitable lenses for the subject. Furthermore, the procedure of this invention, by using a set of novel protocols involved in calculating sphere, cylinder and axis that are easily automated, results in the following desirable features: